Method of installing an electrical transmission cable

ABSTRACT

A method of installing an electrical transmission cable includes providing an electrical transmission cable extending from a first end to a second end. The cable includes a flexible, full tension splice between the first end and the second end. Additionally, the electrical transmission cable includes at least one composite wire. Additionally, the flexible, full tension splice is pulled over a first sheave assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/276,607, filed Mar. 7, 2006, issued as U.S. Pat. No. 7,353,602, thedisclosure of which is incorporated by reference in its entirety herein.

BACKGROUND

Composite wires typically include a matrix material reinforced withsubstantially continuous, longitudinally extending fibers. Examples ofcomposite wires include a metal or polymer matrix material reinforcedwith fibers (e.g., carbon and ceramic fibers). The use of some compositewires in overhead electrical power transmission cables is of particularinterest. Many embodiments of such wires can provide greater powertransfer than traditional transmission cables and have thereby allowedincreased power transfer capacity with existing electrical transmissioninfrastructures.

During installation, transmission cable is typically provided on asupply reel and pulled from the reel over a series of sheaves hangingfrom suspension towers. Care is taken when pulling or otherwisetensioning the cable over the sheave assemblies to avoid bending thecable to a radius less than the minimum bend radius, as excessivetension while bending the cable can result in damage to the cable core,for example. Generally, the amount of bending that is tolerateddecreases as the cable tension increases. The minimum bend strength oftransmission cables including composite wires, however, is typicallyhigher than for traditional transmission cables not utilizing compositewires.

Additionally, electrical transmission cable is not available in infinitelengths, and as such a series of electrical transmission cables isperiodically connected end-to-end (i.e., spliced) in order to provide asufficiently long span of cable. It is desirable for splices in aninstalled electrical transmission cable to be full tension splices.Further, it is desirable to connect ends of a series of cables with fulltension splices prior to pulling the transmission cable over the sheaveassemblies.

Splices used for conventional electrical transmission cables havingsteel core wires are typically rigid compression splices formed ofaluminum and steel tubing. The rigidity of such compression splicesprevents the splices from being pulled over sheaves without a high riskof either permanently bending, deforming, or otherwise causing stressdamage to the splice itself or a risk of damaging the spliced cable, forexample where it transitions into the rigid splice. In particular,“pinch points,” or other small bending radius points are formed at endsof the rigid splice, thereby giving rise to a high risk of transmissioncable damage.

In order to reduce such effects, a splice cover formed of an aluminumtube with rubber bushings at each end of the tube is sometimes disposedover these rigid splices to help reduce damage to the rigid splice andspliced steel core cable. However, this practice is seldom used withsteel core cables due to a remaining risk of damage.

More flexible, full tension splices, such as formed-wire type splices,have been used to connect composite wire cables. However, methods ofpulling such flexible, full tension splices over sheave assemblies havenot previously been recognized or employed. In particular, instead ofpulling a flexible, full tension splice over sheaves, unspliced cable ispulled over the sheaves, and later spliced. Other methods of connectingthe composite wire cables during installation are employed, such asusing temporary wire mesh grips, also described as sock splices, toprovide a temporary mechanical connection between lengths of electricaltransmission cable while the transmission cable is being strung over thesheave assemblies.

The connections formed using these wire mesh grips are relatively lowstrength in comparison with rated breaking strengths of the cable itselfand do not provide any electrical connection. Additionally, even withthis type of wire mesh grip connection, there are limits as to angle,tension, and sheave diameter for which the mesh grip connection andconnected lengths of cable can be effectively pulled into position overa sheave assembly. For example, damage to the cable at the edges of thewire mesh grip is possible during installation.

Following positioning of the transmission cable over the sheaves, thewire mesh grips are typically replaced with permanent, full-tensionsplices used to join the lengths of cable. However, later installationof the splices following positioning of the transmission cable addsinstallation steps (including additional equipment, time, and othercosts) and can be problematic, for example, where the installer does nothave the necessary field access required to install a splice mid-spanbetween lengths of cable.

SUMMARY

One aspect of the invention described herein provides a method ofinstalling an electrical transmission cable. In one embodiment accordingto the invention, a method of installing an electrical transmissioncable includes providing a first cable including at least one compositewire. The first cable has a first end and a second end. A second cableis also provided. The second cable includes at least one composite wire.The second cable also has a first end and a second end. Each of thecomposite wires of the first and second cables includes a plurality ofsubstantially continuous, longitudinally extending fibers in a matrixmaterial. The second end of the first cable is joined to the first endof the second cable using a flexible, full tension splice. The first endof the first cable is guided over a first sheave assembly and is pulledover the first sheave assembly to the second end of the first cable.

In another embodiment according to the invention, a method of installingan electrical transmission cable includes providing an electricaltransmission cable extending from a first end to a second end. The cableincludes a flexible, full tension splice between the first end and thesecond end. The electrical transmission cable includes at least one towof substantially continuous, longitudinally positioned fibers in amatrix. Additionally, the flexible, full tension splice is pulled over afirst sheave assembly.

Surprisingly, Applicants have discovered the ability to install, via asheave assembly, electrical transmission cable having flexible, fulltension splice wherein the cable includes at least one tow ofsubstantially continuous, longitudinally positioned fibers in a matrix,with no significant damage to the cable and splice.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described with reference to theaccompanying drawings wherein like reference numerals refer to likeparts in the several views, and wherein:

FIG. 1 is a schematic view of a method of installing electricaltransmission cable according to one exemplary embodiment of theinvention.

FIGS. 2A-2C illustrate an exemplary flexible, full tension splice from afront view.

FIGS. 3 and 4 are schematic, cross-sections of two exemplary embodimentsof overhead electrical power transmission cables having cores ofcomposite wires.

FIG. 5 is an end view of an exemplary embodiment of a stranded cablewith a maintaining means around the plurality of strands.

FIG. 6 is an end view of an exemplary embodiment of an electricaltransmission cable.

FIG. 7 is a schematic view of an exemplary ultrasonic infiltrationapparatus used to infiltrate fibers with molten metals in accordancewith the present invention.

FIGS. 8, 8A, and 8B are schematic views of an exemplary strandingapparatus used to make cable in accordance with the present invention.

FIG. 9 is a schematic view of an exemplary test apparatus for testingsplices pulled over a test sheave in accordance with the presentinvention.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

Referring to FIG. 1, there is shown exemplary cable installation system10 for stringing transmission cable 12 in an overhead configuration.System 10 includes tensioner 14 for feeding transmission cable 12 undertension, first sheave assembly 16 maintained by first suspension tower18, second sheave assembly 20 maintained by second suspension tower 22,and tugger 24 for pulling transmission cable 12 from tensioner 14 andover first and second sheave assemblies 16, 20. While only two sheaveassemblies are shown, it should be understood that system 10 optionallyincludes any desired number of additional sheave assemblies maintainedby corresponding suspension towers or other appropriate structures.

In one exemplary embodiment, transmission cable 12 includes first cable26, second cable 28, and third cable 30. Transmission cable 12 alsoincludes first splice 32 joining first and second cables 26, 28, andsecond splice 34 joining second and third cables 28, 30. First cable 26extends from leading end 36 maintained by tugger 24 to trailing end 38partially disposed in first splice 32. Second cable 28 extends fromleading end 40 partially disposed in first splice 32 to trailing end 42partially disposed in second splice 34. Third cable 30 similarly extendsfrom leading end 44 partially disposed in second splice 34 to trailingend 46 maintained by tensioner 14. In one exemplary embodiment, each offirst, second, and third cables 26, 28, 30 is at least about 980 feet(about 300 meters) in length, although other dimensions arecontemplated. In some embodiments, each of the first, second, and thirdcables 26, 28, 30 is at least about 1000, 2000, 3000, 4000, 5000, 6000,7000, 8000, 9000, or even at least about 10,000 feet in length.

Additionally, and as will be described in greater detail below withreference to FIGS. 3-6, a transmission cable, including each of first,second, and third cables, includes at least one composite wire includinga plurality of substantially continuous, longitudinally extendingreinforcing fibers in a matrix material.

Typically the fraction of core (i.e., the fraction of core relative tothe whole cable as expressed with respect to the cable cross-section asan area fraction of the core to whole cable) is in a range from about 5%to 30%. In some embodiments the fraction of core relative to the wholecable is at least 2%, at least 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%,25%, 30%, 35%, 40%, 45%, 50%, or even at least 60%.

Exemplary matrix materials include metal matrix materials such asaluminum, titanium, zinc, tin, magnesium, and alloys thereof (e.g., analloy of aluminum and copper), and polymeric matrix materials such asepoxies, esters, vinyl esters, polyimides, polyesters, cyanate esters,phenolic resins, bismaleimide resins and thermoplastics.

Examples of suitable continuous (i.e., having a length that isrelatively infinite when compared to the average fiber diameter) fibersfor making composite wires include aramid fibers, boron fibers, carbonfibers, ceramic fibers, graphite fibers,poly(p-phenylene-2,6-benzobisoxazole), tungsten fibers, and shape memoryalloy (i.e., a metal alloy that undergoes a Martensitic transformationsuch that the metal alloy is deformable by a twinning mechanism belowthe transformation temperature, wherein such deformation is reversiblewhen the twin structure reverts to the original phase upon heating abovethe transformation temperature) fibers. Ceramic fibers include glass,silicon carbide fibers, and ceramic oxide fibers. Typically, the ceramicfibers are crystalline ceramics (i.e., exhibits a discernible X-raypowder diffraction pattern) and/or a mixture of crystalline ceramic andglass (i.e., a fiber may contain both crystalline ceramic and glassphases), although they may also be glass. In some embodiments, the fiberis at least 50 (in some embodiments, at least 55, 60, 65, 70, 75, 80,85, 90, 95, 96, 97, 98, 99, or even 100) percent by weight crystalline.Examples of suitable crystalline ceramic oxide fibers include refractoryfibers such as alumina fibers, aluminosilicate fibers, aluminoboratefibers, aluminoborosilicate fibers, zirconia-silica fibers, andcombinations thereof.

In some embodiments, it is desirable for the fibers to comprise at least40 (in some embodiments, at least 50, 60, 65, 70, 75, 80, 85, 90, 95,96, 97, 98, 99, or even 100) percent by volume Al₂O₃, based on the totalvolume of the fiber. In some embodiments, it is desirable for the fibersto comprise in a range from 40 to 70 (in some embodiments, in a rangefrom 55 to 70, or even 55 to 65) percent by volume Al₂O₃, based on thetotal volume of the fiber.

Further, exemplary glass fibers are available, for example, from CorningGlass, Corning, N.Y. Typically, the continuous glass fibers have anaverage fiber diameter in a range from about 3 micrometers to about 19micrometers. In some embodiments, the glass fibers have an averagetensile strength of at least 3 GPa, 4 GPa, and or even at least 5 GPa.In some embodiments, the glass fibers have a modulus in a range fromabout 60 GPa to 95 GPa, or about 60 GPa to about 90 GPa.

Alumina fibers are described, for example, in U.S. Pat. Nos. 4,954,462(Wood et al.) and 5,185,299 (Wood et al.). In some embodiments, thealumina fibers are polycrystalline alpha alumina fibers, and comprise,on a theoretical oxide basis, greater than 99 percent by weight Al₂O₃and 0.2-0.5 percent by weight SiO₂, based on the total weight of thealumina fibers. In another aspect, some desirable polycrystalline, alphaalumina fibers comprise alpha alumina having an average grain size ofless than 1 micrometer (or even, in some embodiments, less than 0.5micrometer). In another aspect, in some embodiments, polycrystalline,alpha alumina fibers have an average tensile strength of at least 1.6GPa (in some embodiments, at least 2.1 GPa, or even, at least 2.8 GPa),as determined according to the tensile strength test described in U.S.Pat. No. 6,460,597 (McCullough et al.). Exemplary alpha alumina fibersare marketed under the trade designation “NEXTEL 610” by 3M Company, St.Paul, Minn.

Aluminosilicate fibers are described, for example, in U.S. Pat. No.4,047,965 (Karst et al). Exemplary aluminosilicate fibers are marketedunder the trade designations “NEXTEL 440”, “NEXTEL 550”, and “NEXTEL720” by 3M Company of St. Paul, Minn.

Aluminumborate and aluminoborosilicate fibers are described, forexample, in U.S. Pat. No. 3,795,524 (Sowman). Exemplaryaluminoborosilicate fibers are marketed under the trade designation“NEXTEL 312” by 3M Company.

Zirconia-silica fibers as described, for example, in U.S. Pat. No.3,709,706 (Sowman).

Typically, the continuous ceramic fibers have an average fiber diameterof at least about 5 micrometers, more typically, in a range from about 5micrometers to about 20 micrometers; and in some embodiments, in a rangefrom about 5 micrometers to about 15 micrometers.

Typically, the ceramic fibers are in tows. Tows are known in the fiberart and typically include a plurality of (individual) generallyuntwisted fibers (typically at least 100 fibers, more typically at least400 fibers). In some embodiments, tows comprise at least 780 individualfibers per tow, and in some cases, at least 2600 individual fibers pertow, or at least 5200 individual fibers per tow. Tows of various ceramicfibers are available in a variety of lengths, including 300 meters, 500meters, 750 meters, 1000 meters, 1500 meters, and longer. The fibers mayhave a cross-sectional shape that is circular, elliptical, or dogbone.

Exemplary boron fibers are commercially available, for example, fromTextron Specialty Fibers, Inc. of Lowell, Mass. Typically, such fibershave a length on the order of at least 50 meters, and may even havelengths on the order of kilometers or more. Typically, the continuousboron fibers have an average fiber diameter in a range from about 80micrometers to about 200 micrometers. More typically, the average fiberdiameter is no greater than 150 micrometers, most typically in a rangefrom 95 micrometers to 145 micrometers. In some embodiments, the boronfibers have an average tensile strength of at least 3 GPa, and or evenat least 3.5 GPa. In some embodiments, the boron fibers have a modulusin a range from about 350 GPa to about 450 GPa, or even in a range fromabout 350 GPa to about 400 GPa.

Further, exemplary silicon carbide fibers are marketed, for example, byCOI Ceramics of San Diego, Calif. under the trade designation “NICALON”in tows of 500 fibers, from Ube Industries of Japan, under the tradedesignation “TYRANNO”, and from Dow Corning of Midland, Mich. under thetrade designation “SYLRAMIC”.

Exemplary silicon carbide monofilament fibers are marketed, for example,by Specialty Materials, Inc., Lowell, Mass. under the trade designation“SCS-9”, “SCS-6”, and “Ultra-SCS”.

Carbon fibers are available, for example, from Amoco Chemicals ofAlpharetta, Ga. under the trade designation “THORNEL CARBON” in tows of2000, 4000, 5000, and 12,000 fibers, Hexcel Corporation of Stamford,Conn., from Grafil, Inc. of Sacramento, Calif. (subsidiary of MitsubishiRayon Co.) under the trade designation “PYROFIL”, Toray of Tokyo, Japan,under the trade designation “TORAYCA”, Toho Rayon of Japan, Ltd. underthe trade designation “BESFIGHT”, Zoltek Corporation of St. Louis, Mo.under the trade designations “PANEX” and “PYRON”, and Inco SpecialProducts of Wyckoff, N.J. (nickel coated carbon fibers), under the tradedesignations “12K20” and “12K50”. Typically, the continuous carbonfibers have an average fiber diameter in a range from about 4micrometers to about 12 micrometers, about 4.5 micrometers to about 12micrometers, or even about 5 micrometers to about 10 micrometers.

Exemplary graphite fibers are marketed, for example, by BP Amoco ofAlpharetta, Ga., under the trade designation “T-300”, in tows of 1000,3000, and 6000 fibers. Typically, such fibers have a length on the orderof at least 50 meters, and may even have lengths on the order ofkilometers or more. Typically, the continuous graphite fibers have anaverage fiber diameter in a range from about 4 micrometers to about 12micrometers, about 4.5 micrometers to about 12 micrometers, or evenabout 5 micrometers to about 10 micrometers. In some embodiments, thegraphite fibers have an average tensile strength of at least 1.5 GPa, 2GPa, 3 GPa, or even at least 4 GPa. In some embodiments, the graphitefibers have a modulus in a range from about 200 GPa to about 1200 GPa,or even about 200 GPa to about 1000 GPa.

Exemplary tungsten fibers are available, for example, from CaliforniaFine Wire Company, Grover Beach, Calif. Typically, such fibers have alength on the order of at least 50 meters, and may even have lengths onthe order of kilometers or more. Typically, the continuous tungstenfibers have an average fiber diameter in a range from about 100micrometers to about 500 micrometers about 150 micrometers to about 500micrometers, or even from about 200 micrometers to about 400micrometers. In some embodiments, the tungsten fibers have an averagetensile strength of at least 0.7 GPa, 1 GPa, 1.5 GPa, 2 GPa, or even atleast 2.3 GPa. In some embodiments, the tungsten fibers have a modulusgreater than 400 GPa to approximately no greater than 420 GPa, or evenno greater than 415 GPa.

Exemplary shape memory alloy fibers are available, for example, fromJohnson Matthey, West Whiteland, Pa. Typically, such fibers have alength on the order of at least 50 meters, and may even have lengths onthe order of kilometers or more. Typically, the continuous shape memoryalloy fibers have an average fiber diameter in a range from about 50micrometers to about 400 micrometers, about 50 to about 350 micrometers,or even about 100 micrometers to 300 micrometers. In some embodiments,the shape memory alloy fibers have an average tensile strength of atleast 0.5 GPa, and or even at least 1 GPa. In some embodiments, theshape memory alloy fibers have a modulus in a range from about 20 GPa toabout 100 GPa, or even from about 20 GPA to about 90 GPa.

Exemplary aramid fibers are available, for example, from DuPont,Wilmington, Del. under the trade designation “KEVLAR”. Typically, suchfibers have a length on the order of at least 50 meters, and may evenhave lengths on the order of kilometers or more. Typically, thecontinuous aramid fibers have an average fiber diameter in a range fromabout 10 micrometers to about 15 micrometers. In some embodiments, thearamid fibers have an average tensile strength of at least 2.5 GPa, 3GPa, 3.5 GPa, 4 GPa, or even at least 4.5 GPa. In some embodiments, thearamid fibers have a modulus in a range from about 80 GPa to about 200GPa, or even about 80 GPa to about 180 GPa.

Exemplary poly(p-phenylene-2,6-benzobisoxazole) fibers are available,for example, from Toyobo Co., Osaka, Japan under the trade designation“ZYLON”. Typically, such fibers have a length on the order of at least50 meters, and may even have lengths on the order of kilometers or more.Typically, the continuous poly(p-phenylene-2,6-benzobisoxazole) fibershave an average fiber diameter in a range from about 8 micrometers toabout 15 micrometers. In some embodiments, thepoly(p-phenylene-2,6-benzobisoxazole) fibers have an average tensilestrength of at least 3 GPa, 4 GPa, 5 GPa, 6 GPa, or even at least 7 GPa.In some embodiments, the poly(p-phenylene-2,6-benzobisoxazole) fibershave a modulus in a range from about 150 GPa to about 300 GPa, or evenabout 150 GPa to about 275 GPa.

Aramid, carbon, graphite, ceramic, poly(p-phenylene-2,6-benzobisoxazole)fibers (including tows of fibers) typically include an organic sizingmaterial on at least a portion of the outer surfaces of at least some ofthe ceramic oxide fibers. Typically, the sizing material provides anadd-on weight in a range from 0.5 to 10 percent by weight. The sizingmaterial has been observed to provide lubricity and to protect the fiberstrands during handling. It is believed that the sizing tends to reducethe breakage of fibers, reduces static electricity, and reduces theamount of dust during, for example, conversion to a fabric. The sizingcan be removed, for example, by dissolving or burning it away.Preferably, the sizing is removed before forming the matrix compositewire according to the present invention. In this way, before forming thecomposite wire the fibers are free of any sizing thereon.

Exemplary metals for matrix materials are highly pure (e.g., greaterthan 99.95%) elemental aluminum or alloys of pure aluminum with otherelements, such as copper. Typically, the metal matrix material isselected such that the matrix material does not significantly chemicallyreact with the fiber (i.e., is relatively chemically inert with respectto fiber material), for example, to eliminate the need to provide aprotective coating on the fiber exterior. Exemplary metal matrixmaterials include aluminum, zinc, tin, magnesium, and alloys thereof(e.g., an alloy of aluminum and copper). In some embodiments, the matrixmaterial desirably includes aluminum and alloys thereof.

Typically, fibers for metal matrix composites include boron, fibers,carbon fibers, crystalline ceramic containing fibers, graphite fibers,tungsten fibers, and shape memory alloy fibers.

In some embodiments, the metal matrix comprises at least 98 percent byweight aluminum, at least 99 percent by weight aluminum, greater than99.9 percent by weight aluminum, or even greater than 99.95 percent byweight aluminum. Exemplary aluminum alloys of aluminum and coppercomprise at least 98 percent by weight Al and up to 2 percent by weightCu. In some embodiments, useful alloys are 1000, 2000, 3000, 4000, 5000,6000, 7000 and/or 8000 series aluminum alloys (Aluminum Associationdesignations). Although higher purity metals tend to be desirable formaking higher tensile strength wires, less pure forms of metals are alsouseful.

Suitable metals are commercially available. For example, aluminum isavailable under the trade designation “SUPER PURE ALUMINUM; 99.99% Al”from Alcoa of Pittsburgh, Pa. Aluminum alloys (e.g., Al-2% by weight Cu(0.03% by weight impurities)) can be obtained, for example, from BelmontMetals, New York, N.Y. Zinc and tin are available, for example, fromMetal Services, St. Paul, Minn. (“pure zinc”; 99.999% purity and “puretin”; 99.95% purity). For example, magnesium is available under thetrade designation “PURE” from Magnesium Elektron, Manchester, England.Magnesium alloys (e.g., WE43A, EZ33A, AZ81A, and ZE41A), titanium, andtitanium alloys can be obtained, for example, from TIMET, Denver, Colo.

The composite cores and wires typically comprise at least 15 percent byvolume (in some embodiments, at least 20, 25, 30, 35, 40, 45, or even 50percent by volume) of the fibers, based on the total combined volume ofthe fibers and matrix material. More typically the composite cores andwires comprise in the range from 40 to 75 (in some embodiments, 45 to70) percent by volume of the fibers, based on the total combined volumeof the fibers and matrix material.

Typically the average diameter of the core is in a range from about 5 mmto about 15 mm. In some embodiments, the average diameter of coredesirable is at least 1 mm, at least 2 mm, or even up to about 3 mm.Typically the average diameter of the composite wire is in a range fromabout 1 mm to 12 mm, 1 mm to 10 mm, 1 to 8 mm, or even 1 mm to 4 mm. Insome embodiments, the average diameter of composite wire desirable is atleast 1 mm, at least 1.5 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9mm, 10 mm, 11 mm, or even at least 12 mm.

Techniques for making metal and polymeric matrix composite wires areknown in the art. For example, continuous metal matrix composite wirecan be made by continuous metal matrix infiltration processes. Onesuitable process is described, for example, in U.S. Pat. No. 6,485,796(Carpenter et al.), the disclosure of which is incorporated herein byreference. Other processing routes for continuous fiber reinforced metalmatrix composites are, for example, discussed in ASM Handbook Vol. 21,Composites, pp. 584-588 (ASM International, Metals Park, Ohio),published in 2001, the disclosure of which is incorporated herein byreference.

Further, for example, techniques for making metal matrix composite wiresinclude those discussed, for example, in U.S. Pat. Nos. 5,501,906(Deve), 6,180,232 (McCullough et al.), 6,245,425 (McCullough et al.),6,336,495 (McCullough et al.), 6,544,645 (McCullough et al.), 6,447,927(McCullough et al.), 6,460,597 (McCullough et al.), 6,329,056 (Deve etal.), 6,344,270 (McCullough et al.), 6,485,796 (Carpenter et al.),6,559,385 (Johnson et al.), 6,796,365 (McCullough et al.), 6,723,451(McCullough et al.), 6,692,842 (McCullough et al.), 6,913,838(McCullough et al.), 7,131,308 (McCullough et al., 7,093,416 (Johnson etal.); and U.S. Pat. Application Publication Nos. US2004/0190733 A1, US2005/0181228 A1, US 2006/0102377 A1, and US 2006/0102378 A1, thedisclosures of which are incorporated herein by reference for theirteachings on making and using metal matrix composite wires.

Wires comprising polymers and fiber may be made, for example, bypultrusion processes which are known in the art. One example of a fiberreinforced polymer is provided, for example, in PCT application havingpublication No. WO 2003/091008A, published Nov. 6, 2003 and PCTapplication publication having publication No. WO 2005/040017A,published May 6, 2005. Pultrusion methods are further described, forexample, in ASM Handbook Vol. 21, Composites, pp. 550-564 (ASMInternational, Metals Park, Ohio), published in 2001, the disclosure ofwhich is incorporated herein by reference

Typically, fibers for polymeric matrix composites include aramid fibers,boron fibers, carbon fibers, ceramic fibers, graphite fibers,poly(p-phenylene-2,6-benzobisoxazole), tungsten fibers, and shape memoryalloy fibers.

In some embodiments, at least 85% (in some embodiments, at least 90%, oreven at least 95%) by number of the fibers in the core are continuous.

Referring again to FIG. 1, each of first, second, and third cables 26,28, 30 has a rated breaking strength, where an ultimate tensile strengthof cables 26, 28, 30 is greater than or equal to the rated breakingstrength. In general terms, the rated breaking strength is determined bya calculation to define a minimum acceptable strength of a cable (seeStandard Reference ASTM B232, published in 2005).

In one exemplary embodiment, transmission cable 12, including splices32, 34 and the composite wire(s) forming the transmission cable 12, issusceptible to damage, including breakage of the longitudinalreinforcing fibers of the composite wires, according to the following:an amount of tension exerted on transmission cable 12; a diameter oftransmission cable 12; a bend radius of transmission cable 12 about asheave; a composition of cable 12, including types of matrix materials,fiber materials, relative amount of fiber material, and others; and abreak over angle (described in greater detail below) of transmissioncable 12 over the sheave.

Along these lines, in one exemplary embodiment, electrical transmissioncable 12, including each of first, second, and third cables 26, 28, 30has an associated minimum sheave diameter. In particular, the associatedminimum sheave diameter corresponds to a minimum bend radius oftransmission cable 12 while under no mechanical load that can beimparted on transmission cable 12 with no significant damage to thetransmission cable 12. Under mechanical load, the minimum bend radius oftransmission cable 12 is a function of the tension and actual break-overangle of transmission cable 12 over a sheave. As tension and break overangle increase, the minimum bend radius for the transmission cable 12increases. As such, sheave diameter is optionally chosen to be largeenough with this in mind, and larger than the minimum sheave diameter.It should be noted that sheave diameter is also typically bounded byphysical constraints, such as a person's ability to lift the sheaveduring installation or other installation requirements.

In one exemplary embodiment, each of first and second splices 32, 34 isa flexible, full tension splice. In general terms, a “flexible” spliceis able to be bent or curved, for example, bending associated with beingpulled over one or more sheave assemblies, with no significant damage totransmission cable 12, including splices 32, 34. This is to becontrasted with rigid splices, such as compression splices formed bycompressing a steel sleeve onto a core of a length of transmissioncable, and then compressing an aluminum sleeve over the steel sleeve andportions of the transmission cable proximate the aluminum sleeve. Ingeneral terms, such rigid splices are incapable of being pulled over oneor more sheave assemblies with no significant bending damage to therigid splice and/or damage to the transmission cable joined with therigid splice. In particular, a rigid splice pulled over a sheaveassembly is permanently deformed or bent after being pulled over asheave assembly. For additional reference, a “full tension” splice isgenerally one that is capable of withstanding a tension comparable tothe rated breaking strength of transmission cable 12.

With reference to FIGS. 2A-2C, in one exemplary embodiment first splice32 is a full tension, flexible splice. For example, the first splice 32is optionally a formed-wire type splice. In particular, first splice 32includes a plurality of helically wound inner rods 50 wrapped abouttrailing end 38 of first cable 26 and leading end 40 of second cable 28,and a plurality of helically wound outer rods 52 wrapped about theplurality of inner rods 50. With reference to FIG. 2B, groups of three,four, or a desired number of inner rods 50 are sequentially applied tofirst and second cables 26, 28 until a desired number of inner rods 50are disposed about first and second cables 26, 28. With reference toFIG. 2C, groups of three, four, or a desired number of outer rods 52 aresequentially applied over the plurality of inner rods 50 until a desirednumber of outer rods 52 are disposed about the plurality of inner rods50. The pluralities of inner and outer rods 50, 52 are optionally formedof aluminum alloy.

As referenced above, suitable splices include flexible, full tensionsplices, such as formed-wire type splices, including those availablefrom Preformed Line Products of Cleveland, Ohio, under the tradedesignation “THERMOLIGN” (part number of TLSP-795). In one exemplaryembodiment, the splice 32 is large enough to dissipate heat efficiently.Transmission cable formed with composite wires is typically designed torun at high temperatures (e.g., greater than about 200° C.) incomparison to cable having steel core wires (e.g., greater than about100° C. A larger splice is able to help keep the temperature of thesplice relatively low. Thus, the splice 32 is optionally composed of twolayers of helical rods to add additional heat sink capability to thesplice 32. Although suited as a heat sink, the ability of flexible, fulltension splices of the transmission cable 12 to safely pass over asheave is a surprising result due to past experience with damage toother types of splices (e.g., wire mesh connectors). Additionally,successful use of a dual-layer splice configuration is furthersurprising as the dual-layer configuration is otherwise indicative ofconcentrated bending forces at the edges of the splice, rendering thesuccessful results achieved even more surprising.

Again, referring to FIG. 2A-2C, in one exemplary embodiment, secondsplice 34 is formed in a substantially similar manner to first splice32, although first and second splices 32, 34 are optionallysubstantially different in form.

With reference to FIG. 1, tensioner 14 is optionally of a type known inthe art and generally serves to maintain a reel of transmission cable12, also described as a reel length of cable. In particular, tensioner14 is adapted to pay out transmission cable 12 under tension, forexample, using a braking mechanism, to avoid unwinding transmissioncable 12 from a reel too quickly. Also, tension may need to be increasedduring pulling in order to reduce cable sag in order for thetransmission cable 12 to clear obstacles or maintain required clearancelevels (e.g., over highways). For reference, each of first, second, andthird cables 26, 28, 30 optionally corresponds to a reel length oftransmission cable 12, in one exemplary embodiment, although otherlengths are also contemplated.

First sheave assembly 16 is maintained by first suspension tower 18, forexample, hanged from first suspension tower 18, and generally includesan array of sheaves 56 adapted to support transmission cable 12 anddisposed along an arc (e.g., 45 degree arc) to define an overall radiusof curvature R₁ over array of sheaves 56. In this manner, array ofsheaves 56 is optionally used to provide a relatively large radius fortransmission cable 12 to travel over without having to provide a single,relatively large diameter sheave. In one exemplary embodiment, each ofsheaves 56 has a diameter of about 7 inches with array of sheaves 56defining an overall radius of curvature R₁ of about 60 inches. It shouldalso be noted that first sheave assembly 16 is optionally mounted tofirst suspension tower 18, or other appropriate structure, in such amanner that the entire first sheave assembly 16 is able to pivot toaccommodate various lines of entry and exit of transmission cable 12from first sheave assembly 16, as will be described in greater detailbelow. In one exemplary embodiment, first suspension tower 18 is of atype known in the art (e.g., a metal framework tower).

Second sheave assembly 20 is maintained by second suspension tower 22,for example, hanged from second suspension tower 22, and generallyincludes sheave 58. In one exemplary embodiment, sheave 58 has adiameter of about 36 inches, although other dimensions are contemplated.From this, it follows that sheave 58 optionally defines an overallradius of curvature, for example, of about 18 inches. It should also benoted that second sheave assembly 20 is optionally mounted to secondsuspension tower 22 or other appropriate structure in such a manner thatthe entire second sheave assembly 20 is able to pivot to accommodatevarious lines of entry and exit of transmission cable 12 from secondsheave assembly 20, as will be described in greater detail below. In oneexemplary embodiment, second suspension tower 22 is of a type known inthe art (e.g., a metal framework tower). It should also be noted thatsubsequent sheave assemblies (not shown) to first and second sheaveassemblies 16, 20 are also contemplated.

Tugger 24 is optionally of a type known in the art and generally servesto pull transmission cable 12 from tensioner 14. In particular, tugger24 is adapted to exert a tension on transmission cable 12, to pulltransmission cable 12 over first and second sheave assemblies 16, 20, oradditional sheave assemblies as desired.

In terms of relative position, tensioner 14 is optionally spacedlaterally apart from first sheave assembly 16 a distance of about threetimes a height at which the first sheave assembly 16 is maintained. Inturn, in one exemplary embodiment, first and second sheave assemblies16, 20 are spaced apart to define a lateral span, or span distance, in arange from about 200 feet to about 1600 feet, although other dimensionsare contemplated, including from about 200 feet to about 600 feet, about600 feet to about 1500 feet, or even from about 1200 feet to about 1600feet, for example. Furthermore, additional, subsequent sheaveassemblies/towers optionally define a similar span distance, or otherspan distance as particular applications require. Tugger 24 isoptionally spaced laterally apart from second sheave assembly 20 adistance of about three times a height at which second sheave assembly20 is maintained, although other dimensions are also contemplated.

With reference to FIG. 1, and in view of the above, a method ofinstalling transmission cable 12 includes guiding leading end 36 offirst cable 26 over first sheave assembly 16 and pulling first cable 26over first sheave assembly 16. In one exemplary embodiment, a suitableleader (not shown) is attached to leading end 36 of first cable 26, theleader then being pulled by tugger 24 to pull first cable 26 directlyfrom a reel maintained by tensioner 14 over first sheave assembly 16.

As shown by the dotted line, transmission cable 12 defines a line ofentry with first sheave assembly 16 at a tangent line to transmissioncable 12 where transmission cable 12 first enters, or first travelsover, first sheave assembly 16. In turn, transmission cable 12 defines aline of exit with first sheave assembly 16 at a tangent line totransmission cable 12 wherein transmission cable 12 exits, or no longertravels over first sheave assembly 16. An angle between the line ofentry and the line of exit at first sheave assembly 16 is described as afirst break-over angle α of transmission cable 12 over first sheaveassembly 16. In one exemplary embodiment, the larger overall radius ofcurvature R₁ is advantageous as the first break-over angle α isrelatively high. In particular, tensioner 14 from which transmissioncable 12 is directly fed to first sheave assembly 16 is often at a muchlower height than first sheave assembly 16 and is also spaced laterallya relatively small distance from first sheave assembly 16 in comparisonto the span distance between first and second sheave assembly 16, 20,for example. As a result, a relatively high angle of entry into firstsheave assembly 16 is often encountered.

Once tensioner 14 has paid out first cable 26 to trailing end 38, secondcable 28 is optionally spliced, or joined, to first cable 26 with firstsplice 32 being a flexible, full tension splice as reference above. Inone exemplary embodiment, second cable 28 is optionally maintained on aseparate reel from first cable 26, with leading end 40 of second cable28 being joined to trailing end 38 of first cable 26 once first cable 26has been paid out to trailing end 38.

In one exemplary embodiment, first cable 26 is pulled over first sheaveassembly 16 to the trailing end 38 of first cable 26 until first splice32 is ultimately pulled over first sheave assembly 16, for example, tothe position where second splice 34 is shown in FIG. 1. First splice 32is pulled over first sheave assembly 16 at the first break-over angle αand with an associated tension being exerted on first splice 32 andfirst and second cables 26, 28. In one exemplary embodiment, firstsplice 32 is pulled over first sheave assembly 16 with the firstbreak-over angle α in a range from about 10 degrees to about 40 degreesand at a tension in a range from about 5% to about 20% of the ratedbreaking strengths (RBS) of each of the first and second cables 26, 28.It should be noted that other first break-over angles α and tensions arealso contemplated. Although first splice 32 is flexible, some risk ofdamage may be further avoided by increasing the overall radius ofcurvature R₁ to reduce an amount of bending of first splice 32. Forexample, the radius of curvature R₁ is optionally selected to besubstantially greater than half of the minimum sheave diameter oftransmission cable 12.

The method also includes guiding leading end 36 of first cable 26 fromfirst sheave assembly 16 over second sheave assembly 20 and pullingfirst cable 26 over second sheave assembly 20 to trailing end 38 offirst cable 26 to first splice 32. As shown by the dotted line,transmission cable 12 defines a line of entry with second sheaveassembly 20 at a tangent line to transmission cable 12 wheretransmission cable 12 first enters, or first travels over, second sheaveassembly 20. After transmission cable 12 has traversed second sheaveassembly 20, transmission cable 12 defines a line of exit with secondsheave assembly 20 at a tangent line to transmission cable 12 wheretransmission cable 12 exits, or no longer travels over second sheaveassembly 20.

An angle between the line of entry and the line of exit of transmissioncable 12 at second sheave assembly 20 is described as a secondbreak-over angle β of transmission cable 12 over second sheave assembly20. In one exemplary embodiment, the overall radius of curvature ofsheave 58 need not be as large as the overall radius of curvature R₁ ofthe array of sheaves 56 to ensure that first splice 32 is not bentthrough too small of a radius. In particular, where the second sheaveassembly 20 is located between the first sheave assembly 16 and asubsequent, third sheave assembly (not shown), the second break-overangle β is often lower than the first break-over angle α as transmissioncable 12 is fed into second sheave assembly 20 from first sheaveassembly 16, which is often at a more comparable height to second sheaveassembly 20 in comparison to a relative height of tensioner 14, andwould feed out to the third sheave assembly which would also be at amore comparable height to the second sheave assembly 20. In other words,the “tower-to-tower,” or “sheave-to-sheave,” angles are typically muchsmaller than the first “ground-to-tower,” or “ground-to-sheave,” angleand the last “tower-to-ground,” or “sheave-to-ground,” angle.

First cable 26 is optionally pulled over first sheave assembly 16 totrailing end 38 and first splice 32 is pulled over second sheaveassembly 20, for example, to the position represented generally inFIG. 1. First splice 32 is pulled over second sheave assembly 20 at thesecond break-over angle β and with an associated tension being exertedon first and second cables 26, 28. In one exemplary embodiment, firstsplice 32 is pulled over second sheave assembly 20 at a secondbreak-over angle β in a range from about 10 degrees to about 40 degreesand at a tension in a range from about 5% to about 20% of the ratedbreaking strengths (RBS) of each of first and second cables 26, 28. Itshould be noted that other second break-over angles β and tensions arealso contemplated. Although first splice 32 is flexible, some risk ofdamage may be further avoided by increasing the overall diameter ofsheave 58 to reduce an amount of bending of first splice 32. In oneexemplary embodiment, the diameter of sheave 58 of second sheaveassembly 20 is selected to be substantially greater than the minimumsheave diameter of transmission cable 12.

Although first splice 32 is shown as being pulled over two sheaveassemblies, in one exemplary embodiment first splice 32 is pulled overadditional sheave assemblies, for example, sheave assembliessubstantially similar to first or second sheave assemblies 18, 20.Additionally, in one exemplary embodiment, second splice 34 is formedbetween second and third cables 28, 30 in a substantially similar mannerto that described in association with first splice 32. Additionally,second splice 34 is optionally pulled over first sheave assembly 16,second sheave assembly 20, or any number of subsequent sheaveassemblies, in a substantially similar manner to that described inassociation with first splice 32.

The system and method described above provide various advantages. Forexample, a permanent, flexible, full-tension splice is employed betweenlengths of cable, rather than pulling transmission cable 12 usingtemporary mechanical connectors, such as wire mesh grips, also describedas sock splices. In this manner, a permanent splice need not beinstalled at some later time, reducing installation steps and increasingefficiency. Furthermore, problems associated with installation ofpermanent splices following positioning of the cable are reduced, forexample, where the installer of transmission cable 12 does not have thenecessary field access required to install a splice mid-span betweensheave assemblies.

As referenced above, cables including composite wires are particularlyuseful in overhead electrical power transmission cables. Transmissioncable 12 according to the present invention may be homogeneous (i.e.,including only one type of composite wire) or nonhomogeneous (i.e.,including a plurality of secondary wires, such as metal wires). As anexample of a nonhomogeneous cable, a core of transmission cable 12 caninclude a plurality of composite wires including longitudinallypositioned reinforcing fibers with an outer shell that includes aplurality of secondary wires (e.g., aluminum wires). Cables according tothe present invention can include metal matrix material or polymermatrix material composite wires, for example.

Additionally, cables according to the present invention can be stranded.A stranded cable typically includes a central wire and a first layer ofwires helically stranded around the central wire. Cable stranding is aprocess in which individual strands of wire are combined in a helicalarrangement to produce a finished cable (see, e.g., U.S. Pat. Nos.5,171,942 (Powers) and 5,554,826 (Gentry)). The resulting helicallystranded wire rope provides far greater flexibility than would beavailable from a solid rod of equivalent cross sectional area. Thehelical arrangement is also beneficial because the stranded cablemaintains its overall round cross-sectional shape when the cable issubject to bending in handling, installation and use. Helically woundcables may include as few as 7 individual strands to more commonconstructions containing 50 or more strands.

One exemplary electrical power transmission cable, or transmissioncable, according to the present invention is shown in FIG. 3, whereelectrical power transmission cable according to the present invention130 may be core 132 of nineteen individual composite (e.g., metal matrixcomposite) wires 134 surrounded by jacket 136 of thirty individual metalwires (e.g., aluminum or aluminum alloy wires) 138. Likewise, as shownin FIG. 4, as one of many alternatives, overhead electrical powertransmission cable according to the present invention 140 may be core142 of thirty-seven individual composite (e.g., metal matrix composite)wires 144 surrounded by jacket 146 of twenty-one individual metal(aluminum or aluminum alloy) wires 148.

FIG. 5 illustrates yet another exemplary embodiment of stranded cable80. In this embodiment, the stranded cable includes central composite(e.g., metal matrix composite) wire 81A and first layer 82A of composite(e.g., metal matrix composite) wires that have been helically woundabout central composite (e.g., metal matrix composite) wire 81A. Thisembodiment further includes a second layer 82B of composite (e.g., metalmatrix composite) wires 81 that have been helically stranded about firstlayer 82A. Any suitable number of composite (e.g., metal matrixcomposite) wires 81 may be included in any layer. Furthermore, more thantwo layers may be included in stranded cable 80 if desired.

Cables according to the present invention can be used as a bare cable orthey can be used as the core of a larger diameter cable. Also, cablesaccording to the present invention may be a stranded cable of aplurality of wires with a maintaining means around the plurality ofwires. The maintaining means may be a tape overwrap (see, e.g., tapeoverwrap 83 shown in FIG. 5), with or without adhesive, or a binder.

Stranded cables according to the present invention are useful innumerous applications. Such stranded cables are believed to beparticularly desirable for use in overhead electrical power transmissioncables due to their combination of low weight, high strength, goodelectrical conductivity, low coefficient of thermal expansion, high usetemperatures, and resistance to corrosion.

An end view of one exemplary embodiment of such a transmission cable isillustrated in FIG. 6 as transmission cable 90. Transmission cable 90includes core 91 which can be any of the stranded cores describedherein. Power transmission cable 90 also includes at least one conductorlayer about stranded core 91. As illustrated, power transmission cableincludes two conductor layers 93A and 93B. More conductor layers may beused as desired. In some embodiments, each conductor layer comprises aplurality of conductor wires. Suitable materials for the conductor wiresinclude aluminum and aluminum alloys. The conductor wires may bestranded about stranded core 91 by suitable cable stranding equipment asis known in the art.

In other applications, in which the stranded cable is to be used as afinal article itself, or in which it is to be used as an intermediaryarticle or component in a different subsequent article, it is desirablethat the stranded cable be free of electrical power conductor layersaround plurality of metal matrix composite wire 81.

Additional details regarding cables made from composite wires aredisclosed, for example, in U.S. Pat. Nos. 6,180,232 (McCullough et al.),6,245,425 (McCullough, et al.), 6,329,056 (Deve, et al.), 6,336,495(McCullough et al.), 6,344,270 (McCullough et al.), 6,447,927(McCullough et al.), 6,460,597 (McCullough et al.), 6,485,796 (Carpenteret al.), 6,544,645 (McCullough et al.), 6,559,385 (Johnson et al.),6,692,842 (McCullough et al.), 6,723,451 (McCullough et al.), 6,796,365(McCullough et al.), 6,913,838 (McCullough et al.), 7,131,308(McCullough et al., 7,093,416 (Johnson et al.); and U.S. Pat.Application Publication Nos. US2004/0190733 A1, US 2005/0181228 A1, US2006/0102377 A1, and US 2006/0102378 A1; and PCT applications havingpublication Nos. WO 97/00976, published May 21, 1996, WO 2003/091008A,published Nov. 6, 2003, and WO 2005/040017A, published May 6, 2005.Aluminum matrix composite containing cables are also available, forexample, from 3M Company under the trade designation “795 kcmil ACCR”.

Advantages and embodiments of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. All parts andpercentages are by weight unless otherwise indicated.

EXAMPLES Example 1

The wire for Example 1 cable was prepared as follows. The wire was madeusing apparatus 60 shown in FIG. 7. Seven (7) tows of 10,000 denieralpha alumina fiber (marketed by the 3M Company, St. Paul, Minn. underthe trade designation “NEXTEL 610”) were supplied from supply spools 62,collimated into a circular bundle, and heat-cleaned by passing through 3meters (9.8 foot) long alumina tube 63 heated to 1100° C. at 549 cm/min(216 in./min). Heat-cleaned fibers 61 were then evacuated in vacuumchamber 64 before entering crucible 65 containing melt (molten metal) 75of metallic aluminum (99.99% Al) matrix material (obtained from BeckAluminum Co., Pittsburgh, Pa.). The fibers were pulled from supplyspools 62 by caterpuller 70. Ultrasonic probes 66, 66A were positionedin melt 75 in the vicinity of the fiber to aid in infiltrating melt 75into tows of fibers 61. The molten metal of wire 71 cooled andsolidified after exiting crucible 65 through exit die 68, although somecooling likely occurred before wire 71 fully exited crucible 65.Further, cooling of wire 71 was enhanced by streams of air deliveredthrough cooling device 69 that impinged on wire 71 at a flow rate of 160liters per minute. Wire 71 was collected onto spool 72.

Fibers 61 were evacuated before entering melt 75. The pressure in thevacuum chamber was about 200 millitorr. Vacuum system 64 had a 25 cmlong alumina entrance tube sized to match the diameter of the bundle offiber 61. Vacuum chamber 64 was 21 cm long, and 10 cm in diameter. Thecapacity of the vacuum pump was 0.37 m³/minute. The evacuated fibers 61were inserted into the melt 75 through a tube on the vacuum system 64that penetrated the metal bath (i.e., the evacuated fibers 61 were undervacuum when introduced into the melt 75). The inside diameter of theexit tube matched the diameter of the fiber bundle 61. A portion of theexit tube was immersed in the molten metal to a depth of 3 mm (0.125inch).

Infiltration of the molten metal 75 into the fibers 61 was enhanced bythe use of vibrating horns 66, 66A positioned 19.8 cm (7.8 inch) apart,and 3.2 cm (1.25 inch) into the molten metal 75 so that the horns werein close proximity to the fibers 61. Horns 66, 66A were driven tovibrate at 19.7 kHz and an amplitude in air of 0.018 mm (0.0007 inch).Horns 66, 66A were connected to titanium waveguides (machined from 31.8mm (1.25 inch) diameter titanium Ti6-4 rod stock from TitaniumIndustries, Chicago, Ill.) via a heat shrink fit to another titaniumwaveguides (i.e., there were four titanium waveguides used) that wereeach (i.e., the latter two titanium waveguides) in turn connected to anultrasonic booster (i.e., there were two ultrasonic boosters), which inturn were connected to a transducer (i.e., there were two transducers;the ultrasonic booster and ultrasonic transducer were obtained fromSonics & Materials, Danbury, Conn.).

Fibers 61 were within 1.3 mm of the horn tips with respect to the fibercenterline. The horn tips were, made of a mixture of silicon nitride andalumina (“SIALON”; obtained from Consolidated Ceramics, Blanchester,Ohio). The ceramic horn tips were fashioned into a cylinder 30.5 cm (12inch) in length and 2.5 cm (1 inch) in diameter. The ceramic horn tipswere waffled with a cross-hatched 900 “V” groove, (0.5 mm (0.020 inch)deep, with center to center distance of 0.25 cm (0.1 inch). The cylinderwas tuned to the desired vibration frequency of 19.7 kHz by altering itslength.

Molten metal 75 was degassed (e.g., reducing the amount of gas (e.g.,hydrogen) dissolved in the molten metal) prior to infiltration. Aportable rotary degassing unit (obtained from Brumund Foundry, Inc,Chicago, Ill.) was used. The gas used was Argon, the Argon flow rate was1.05 liters per minute, the speed was provided by the air flow rate tothe motor set at 50 liters per minute, and duration was 60 minutes.

Silicon nitride exit die 68 was configured to provide the desired wirediameter. The internal diameter of the exit die was 2.08 mm (0.082inch).

The stranded core was stranded on stranding equipment at Wire RopeCompany in Montreal, Canada. The cable had one wire in the center, sixwires in the first layer with a left hand lay and then twelve wires in asecond (outer) layer with a right hand lay. Prior to being helicallywound together, the individual wires were provided on separate bobbinswhich were then placed in two motor driven carriages of the strandingequipment. The first carriage held the six bobbins for the first layerof the finished stranded cable and the second carriage held the twelvebobbins for the second layer of the stranded cable. The wires of eachlayer were brought together at the exit of the carriage and arrangedover the preceding wire or layer. During the cable stranding process,the central wire, was pulled through the center of the carriage, witheach carriage adding one layer to the stranded cable. The individualwires added in each layer were simultaneously pulled from theirrespective bobbins while being rotated about the central axis of thecable by the motor driven carriage. The result was a helically strandedcore.

The stranded core was wrapped with adhesive tape using conventionaltaping equipment (Model 300 Concentric Taping Head from Watson MachineInternational, Paterson, N.J.). The tape backing was aluminum foil tapewith fiberglass, and had a pressure sensitive silicone adhesive(obtained under the trade designation “FOIL/GLASS CLOTH TAPE 363” from3M Company, St. Paul, Minn.). The total thickness of tape 18 was 0.18 mm(0.0072 inch). The tape was 1.90 cm (0.75 inch) wide.

The diameter of the finished core was nominally 10.4±0.25 mm (0.410±0.01inch) and the lay lengths of the stranded layers were nominally 41.1 cm(16.2 inches) with a left-hand lay for the first layer and 68.8 cm (27.1inches) with a right-hand lay for the second (outer) layer.

The aluminum alloy wires were prepared from aluminum/zirconium rod (9.8mm (0.386 inch) diameter); obtained from Lamifil N.V., Hemiksem,Belgium, under the trade designation “ZTAL”). Minimum propertyrequirements are for a tensile strength of 120.0 MPa (17,400 psi), anelongation of 10.0%, and an electrical conductivity of 60.5% IACS. Therods were drawn down at room temperature using five dies as is known inthe art. The drawing dies (obtained from Bronson & Bratton, Burr Ridge,Ill.) were made of tungsten carbide and had an as-received highlypolished die surface. The geometry of the tungsten carbide die had a 60°entrance angle, a 16-180 reduction angle, a bearing length 30% of thedie diameter, and a 60° back relief angle. The die was lubricated andcooled using a drawing oil. The drawing system delivered the oil at arate set in the range of 60-100 liters per minute per die, with thetemperature set in the range of 40-50° C.

This wire was then wound onto bobbins. Various properties of theresulting wires made from the respective 6 feedstock rods are listed inTable 2, below.

TABLE 2 Feedstock Rod Diameter, Tensile Elon- Con- From which mmstrength, gation, ductivity, Wire Was Made (inch) MPa (psi) % IACS %Inner Layer 1 4.44 (0.1748) 166.6 (24,168) 4.9 60.4 2 4.43 (0.1744)170.1 (24,670) 4.9 60.6 3 4.43 (0.1744) 169.5 (24,586) 5.5 60.3 4 4.43(0.1744) 168.4 (24,418) 4.9 60.7 5 4.43 (0.1744) 171.3 (24,849) 4.9 60.46 4.43 (0.1744) 174.5 (25,309) 4.9 60.0

The cable used for sheave testing was made as a batch of eight cables,using the wires from the 6 different wires referred to in Table 2,above. There were 26 bobbins loaded into the stranding equipment, 10wires for stranding the first inner layer, 16 wires for stranding thesecond outer layer, and wire was taken from a subset of these fortesting, which were the “sampled bobbins”.

A cable was made by Nexans, Weyburn, SK, Canada, using a conventionalplanetary stranding machine and the core and (inner and outer) wires. Aschematic of the apparatus 180 for making cable is shown in FIGS. 8, 8A,and 8B.

Spool of core 181 was provided at the head of a conventional planetarystranding machine 180, wherein spool 181 was free to rotate, withtension capable of being applied via a braking system. The tensionapplied to the core during payoff was 45 kg (100 lbs.). The core wasinput at room temperature (about 23° C. (73° F.)). The core was threadedthrough the center of the bobbin carriages 182, 183, through closingdies 184, 185, around capstan wheels 186 and attached to conventionaltake-up spool ((152 cm (60 inch diameter)) 187.

Prior to application of outer stranding layers 189, individual wireswere provided on separate bobbins 188 which were placed in a number ofmotor driven carriages 182, 183 of the stranding equipment. The range oftension required to pull the wire 89 from the bobbins 188 was set to bein the range 11-14 kg (25-30 lbs.). Stranding stations consist of acarriage and a closing die. At each stranding station, wires 189 of eachlayer were brought together at the exit of each carriage at closing die184, 185, respectively and arranged over the central wire or over thepreceding layer, respectively. Thus, the core passed through twostranding stations. At the first station 10 wires were stranded over thecore with a left lay. At the second station 16 wires were stranded overthe previous layer with a right lay.

The core material and wires for a given layer were brought into contactvia a closing die 184, 185, as applicable. The closing dies werecylinders (see FIGS. 8A and 8B) and were held in position using bolts.The dies were made of nylon and were capable of being fully closed.

The finished cable was passed through capstan wheels 186, and ultimatelywound onto (107 cm diameter (42 inch)) take-up spool 187.

The inner layer consisted of 10 wires with an outside layer diameter of0.19.3 mm (0.760 inch), a mass per unit length of the inner layer of 422kg/km (283.2 lbs./kft.) with the left hand lay of 27.4 cm (10.8 inch).The closing blocks (made from nylon) for the inner layer were set at aninternal diameter of 19.3 mm (0.760 inch). Thus the closing blocks wereset at exactly the same diameter as the cable diameter.

The outer layer consisted of 16 wires with an outside layer diameter of28.1 mm (1.106 inch), a mass per unit length of the outer aluminum layerof 691.0 kg/km (463.1 lbs./kft.) with the right hand lay of 30 cm (11.8inch). The total mass per unit length of aluminum alloy wires was 1109kg/km (743.6 lbs./kft.), total mass per unit length of the core was229.0 kg/km (153.5 lbs./kft.) and the total conductor mass per unitlength was 1342 kg/km (899.8 lbs./kft.). The closing blocks (made fromnylon) for the outer layer were set at an internal diameter of 28 mm(1.1 inch). Thus the closing blocks were set at exactly the samediameter as the final cable diameter.

The inner wire and outer wire tension (as pay-off bobbins) was measuredusing a hand held force gauge (obtained from McMaster-Card, Chicago,Ill.) and set to be in the range of 13.5-15 kg (29-33 lbs.) and the corepay-off tension was set by brake using the same measurement method asthe bobbins at about 90 kg (198 lbs.). Further, no straightener wasused, and the cable was spooled. The core was input at room temperature(about 23° C. (73° F.)).

With reference to FIG. 9, a test fixture 200 was employed to test theresulting conductor cable 202 using the following test method. A 12.2meter (40 feet) section of conductor cable 202 was laid out straight onthe floor. A single 49 meter (160 feet) piece of low stretch rope 204(obtained from Wall Industries, Spencer, S.C., under the tradedesignation “UNILINE”) was attached to each end of conductor cable 202using pull grips (not shown), forming a 61 meter (200 feet) loop. Inparticular, at each end of the low stretch rope, wire mesh grips wereinstalled, and at each end of the conductor cable section, wire meshgrips were attached. The loops of the wire mesh grip at the ends of rope204 and conductor cable 202 were brought together and attached togetherusing a swivel coupling (not shown). The conductor cable section of theloop was then cut in half and reconnected with flexible, full tensionsplice 206 (obtained from Preformed Line Products, Cleveland, Ohio underthe trade designation “THERMOLIGN”; part number TLSP-795). Ends ofsplice 206 were taped to prevent rods of splice 206 from catching onsheave 214.

The ensuing loop of low stretch rope 204, conductor cable 202, andsplice 206 were then installed on test fixture 200. Test fixture 200consisted of three sheaves, first, fixed drive sheave 210 for drivingthe loop of rope 204, conductor cable 202, and splice 206 in thedirection indicated by the arrows, second variable tension sheave 212for imparting a force (F) on the loop, and third sheave 214 fitted witha load cell 216. First fixed drive sheave 210 had a diameter of 140 cm(55 inch), second variable tension sheave 212 had a diameter of 140 cm(55 inch), and third sheave 214 had a diameter of 92 cm (36 inch).Conductor cable 202 and splice 206 were pulled over third sheave 214 ata break over angle θ of 18.7 degrees at a % RBS Tension in the range of16.3% to 17.3%.

Break over angle θ was set either by changing a position of secondsheave 212 or by adjusting a length of the loop of rope 204, conductorcable 202, and splice 204. Anticipated break over angles were set in thefield, and actual break over angles were later accurately measured byimage processing of digital photographs of the test fixture 200. The %RBS Tension (T) on the loop was monitored using resultant force (R)measured by the load cell 216 using the equation T=R/2 sin(θ/2). Duringtesting, the % RBS tension fluctuated due to stretch of the loop and wasadjusted with second sheave 212 during testing.

Conductor cable 202 and splice 206 were cycled over third sheave 214 bydrawing the conductor cable 202 and splice 206 over third sheave 214,stopping conductor cable 202 and splice 206 prior to passing over firstor second sheaves 210, 212, then removing the tension on the loop ofrope 204, conductor cable 202, and splice 206, and resetting the loop.During cycling, test operators listened for any acoustic noise, such as“clicks” which would be indicative of composite wire core breakage.After twenty cycles of conductor cable 202 and splice 206 over thirdsheave 214, conductor cable 202 and splice 206 were disassembled and theconductor cable wires were visually inspected for damage. Visualinspection of the wires indicated there was no significant damage.Additionally, the splice 206 showed no signs of distortion or permanentdeformation. No clicking or other audible cues were observed either.Hence it was concluded there was no significant damage to the cable orsplice.

Example 2

The procedure described in Example 1 was followed for Example 2 with theexception that the third sheave 214 was a roller array of six 18 cm (7inch) diameter sheaves disposed along a 45 degree arc to define anoverall effective radius of 60 inches and the testing was performed witha break over angle θ of 29.6 degrees and a % RBS tension in the range of9.7% to 11%. After three cycles over third sheave 214, conductor cable202 and splice 206 were disassembled and the conductor cable wires werevisually inspected for damage. No clicking or other audible cues wereobserved. Visual inspection of the wires indicated there was nosignificant damage. Additionally, the splice 206 showed no signs ofdistortion or permanent deformation. Hence it was concluded there was nosignificant damage to the cable or splice.

Example 3

The procedure described in Example 2 was followed for Example 3 with theexception that third sheave 214 was the same roller array of six 18 cm(7 inch) diameter sheaves with the testing performed at a break overangle of 33.8 degrees and a % RBS tension in the range of 16.6% to17.4%. After three cycles over third sheave 214, conductor cable 202 andsplice 206 were disassembled and the conductor cable wires were visuallyinspected for damage. No clicking or other audible cues were observed.Visual inspection of the wires indicated there was no significantdamage. Additionally, the splice 206 showed no signs of distortion orpermanent deformation. Hence it was concluded there was no significantdamage to the cable or splice.

Example 4

The procedure described in Example 2 was followed for Example 4 with theexception that third sheave 214 was the same roller array of six 18 cm(7 inch) diameter sheaves with the testing performed at a break overangle of 39 degrees and a % RBS tension in the range of 10.1% to 10.6%.After three cycles over the test sheave, conductor cable 202 and splice206 were disassembled and the conductor cable wires were visuallyinspected for damage. No clicking or other audible cues were observed.Visual inspection of the wires indicated there was no significantdamage. Additionally, splice 206 showed no signs of distortion orpermanent deformation. Hence it was concluded there was no significantdamage to the cable or splice.

Comparative Example A

The procedure described in Example 1 was followed for ComparativeExample A with the exception that third sheave 214 had a diameter of 71cm (28 inch) with the testing performed at a break over angle of 33degrees and a % RBS tension in the range of 8.7% to 10.1%. Additionally,there was no splice applied, the conductor cable section beingcontinuous. Also, the loop was not unloaded and reversed after eachcycle but was driven continuously around the entire loop while under thetest tension. After the first cycle, an audible “click” was heard asconductor cable 202 left third sheave 214 in the region of the wire meshgrip on the trailing end of conductor cable 202. The test was stoppedafter 5 cycles. After five cycles over third sheave 214, conductor cable202 was disassembled and the conductor cable wires were visuallyinspected for damage. Visual inspection of the wires indicated there wasone broken core wire at the transition from conductor cable 202 into thewire mesh grip on the trailing end side of conductor cable 202. Theremaining wires were intact and indicated no other significant damage.Hence it was concluded there was significant damage to conductor cable202 due to the presence of the wire-mesh grip.

Comparative Example B

The procedure described in Comparative Example A was followed forComparative Example B with the exception that although third sheave 214had a the same diameter of 71 cm (28 inch), the testing was performed ata break over angle of 33 degrees and a % RBS tension in the range of7.3% to 7.9%. After twenty cycles over third sheave 214, conductor cable202 was disassembled and the conductor cable wires were visuallyinspected for damage. No clicking or other audible cues were observed.Visual inspection of the wires indicated there was no significantdamage. Hence it was concluded there was no significant damage to theconductor cable 202.

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat a variety of alternate and/or equivalent implementations may besubstituted for the specific embodiments shown and described withoutdeparting from the scope of the present invention. This application isintended to cover any adaptations or variations of the specificembodiments discussed herein. Therefore, it is intended that thisinvention be limited only by the claims and the equivalents thereof.

1. A method of installing an electrical transmission cable, the methodcomprising: providing an electrical transmission cable extending from afirst end to a second end, the cable including a flexible, full tensionsplice between the first end and the second end, the electricaltransmission cable comprising at least one tow of substantiallycontinuous, longitudinally positioned fibers in a matrix material; andpulling the flexible, full tension splice over a first sheave assembly.2. The method of claim 1, further comprising: pulling the flexible, fulltension splice over at least one subsequent sheave assembly.
 3. Themethod of claim 1, wherein the electrical transmission cable extends alength of at least about 980 feet from the first end to the second end.4. The method of claim 1, wherein the flexible, full tension splicecomprises a plurality of helically-wound rods.
 5. The method of claim 1,wherein the tows of substantially continuous, longitudinally positionedfibers are selected from the group consisting of ceramic fibers, carbonfibers, and mixtures thereof, and further wherein the matrix material isselected from the group consisting of aluminum and alloys thereof,titanium and alloys thereof, zinc and alloys thereof, tin and alloysthereof, magnesium and alloys thereof, and polymers.
 6. The method ofclaim 1, wherein the electrical transmission cable is provided on a reelpositioned at a first height, and further wherein the first sheaveassembly is maintained at a second height greater than the first heightof the reel.
 7. The method of claim 1, wherein the electricaltransmission cable has an associated minimum sheave diameter, andfurther wherein first sheave has a larger diameter than the nominalsheave diameter.